Field of the Invention
Aspects of the present invention generally relate to an optical scanning device equipped with a plurality of optical-system components including a light deflector, which deflects a light beam, and a detection unit, which detects timing at which a light beam passes.
Description of the Related Art
An optical scanning device, which is used for an image forming apparatus, such as a laser printer, uses a light deflector, which is composed of, for example, a rotary polygonal mirror, to perform deflection scanning with a laser light beam emitted from a light source according to an image signal. The laser light beam subjected to deflection scanning is led to a beam detection (BD) sensor (a beam detector), which serves as a light detection unit (a light receiving element), so as to control timing of the scanning start position on a surface to be scanned. The laser light beam is moved while being focused in a spot shape on a photosensitive recording medium by an imaging optical system (a scanning lens) having an fθ characteristic. The writing start timing of optical scanning is a predetermined time after the BD sensor outputs a synchronization signal.
Japanese Patent No. 4109878 discusses a configuration in which the above-mentioned BD sensor is mounted on a circuit board.
In the configuration discussed in Japanese Patent No. 4109878, the BD sensor, serving as an element, is mounted on the circuit board from a surface (first surface) of the circuit board on the side at which to receive a laser light beam. Then, the BD sensor receives a laser light beam through a through-hole provided in an optical box to which the circuit board is fixed. In recent years, it has been considered that, to reduce an apparatus size and lower costs, the BD sensor, serving as a light receiving member, is mounted on the circuit board from a surface (second surface) of the circuit board opposite to the first surface.